While hydronic baseboards holders through which hot water is circulated have been connected to rigid piping systems over many years, more recently the development of PEX tubing for hydronic applications has led to the connection of baseboards in the hydronic system by such tubing through fittings between an end of the finned-tube element and the PEX tubing. Such fittings may be threaded brass fittings soldered to the copper tube of the finned-tube element and joined to the PEX tubing by a compression nut.
It has been found in practice that additional bracing may be required for the end of the finned-tube element which is connected to the PEX tubing and which in earlier hydronic systems was held rigidly by attachment to fixed piping systems.
In other words the use of flexible piping like PEX tubing has mandated additional bracing at the point at which the PEX tubing is connected to the finned-tube element of a baseboard heater.